1. Field of the Invention
The present invention relates to mixers for immiscible fluids, and more particularly to mixers for mixing fuel and water in gas turbine engines.
2. Description of Related Art
A variety of devices and methods are known in the art for injecting fuel into gas turbine engines. Of such devices, many are directed to injecting fuel into combustors of gas turbine engines while reducing undesirable emissions. Modern gas turbine engine designs use high temperature combustion for thermal efficiency throughout a range of engine operating conditions. High temperature combustion minimizes emissions of some undesired gaseous combustion products, such as carbon monoxide (CO) and unburned hydrocarbons (UHC), and particulates, among other things. However, high temperature combustion also tends to increase the production of nitrogen oxides (NOX). Thus measures must be taken to provide thermally efficient operation within a temperature range that minimizes NOX, CO, and UHC.
One method often used to reduce unwanted NOX emissions is to lower the temperature of combustion by injecting water into the combustor with the fuel. The water absorbs heat in the combustor, lowering the temperature of fuel combustion and reducing unwanted NOX emissions. Injecting water into the combustor is particularly advantageous in non-flight applications such as industrial gas turbine engines, where water supplies are readily available.
Injecting water into the combustor of a gas turbine engine presents challenges related to uniform distribution of water and fuel within the combustor. Some approaches to this problem have been to provide fuel injectors for the fuel that are separate from the injectors for the water, or to provide both fuel and water circuits within each injector with separate injection ports for fuel and water. These approaches attempt to provide uniform spray patterns of both fuel and water within the combustor, but add to the complexity and cost of the engine and maintenance. Another approach has been to inject water and fuel simultaneously through a single set of injectors by mingling the water and fuel together in the fuel lines prior to injection. The problem with this approach is that hydrocarbon fuel oil and water are immiscible. Simply mingling the two fluids together in a fuel line does not result in a uniform distribution of the fuel-water mixture at the injectors, since the two fluids tend to arrive at the injectors in a highly unmixed state.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still an need in the art for mixers that allow for improved mixing of immiscible fluids. There also remains a need in the art for such mixers that are easy to make and use. The present invention provides a solution for these problems.